Method and apparatus for electrolytically producing highly pure gallium



LEIBENZEDEF! METHOD AND APPARATUS FOR ELECTROLYTICALLY PRODUCING HIGHLY PURE GALLIUM Filed June 15, 1964 June 13, 1967 2 Sheets-Sheet 1 iiwir June 13. 1967 s. LEmENzEnm 3,325,380

METHOD AND APPARATUS FOR ELEG'IROLYTICALLY PRODUCING HIGHLY PURE GALLIUM Filed June 15, 1964 2 Sheets-Sheet 2 FIG, 2

United States Patent 3,325,380 METHOD AND APPARATUS FOR ELECTRO- LYTICALLY PRODUCING HIGHLY PURE GALLIUM Siegfried Leibenzeder, Erlangen, Germany, assignor to Siemens-Schuckertwerke Aktiengesellschaft, Berlin-Siemensstadt, Germany, a corporation of Germany Filed June 15, 1964, Ser. No. 375,211 Claims priority, application Germany, June 15, 1963, S 85,697 2 Claims. (Cl. 204-59) My invention relates to the production of highly pure gallium by eleotrolytical precipitation from a solution of a gallium complex of the type Ga(GaX in a nonaqueous organic solvent, the symbol X denoting a halogen element. A method of this kind is described in my copending application Ser. No. 141,381, filed Sept. 28, 1961, now US. Patent No. 3,170,856, and the corresponding German Patent 1,141,461.

This method is predicated upon the discovery that gallium complexes of the above-mentioned type in nonaqueous organic solvents, for example benzene, toluene or xylene, exhibit good solubility and electrical conductance and that gallium can be electrolytically separated from such solutions. This was all the more unexpected as the mentioned complexes have a salt-like constitution.

It is an object of my invention to further improve methods of this type by alfording the use of electrolytes that can be prepared at lower cost.

I have found that this is achieved by modifying the above-described electrolytic gallium-production process in the following manner.

According to the invention, the complex-bond gallium in the abovementioned gallium complex of the type Ga(GaX is substituted by aluminum. In other words, the method according to the invention is performed by using the complex Ga(AlX The solubility of this complex, for example if the halogen X is bromine, in benzene at 20 C. is about 1200 g. liter. The specific electric conductivities of electrolytes thus employed at a concentration of 60% by weight of Ga(AlBr and respective temperatures of 22 and 40 C. have been measured respectively at 0.015 and 0.02 (ohm cmf The production is effected in accordance with the following reaction equation.

The complex is extracted with a non-aqueous organic solvent, preferably aromatic solvents, for example benzene, toluene or xylene, in an extractor such as a Soxhlet apparatus, thus arriving at the electrolyte according to the invention.

The invention will be further described with reference to the drawings in which:

FIG. 1 shows schematically an electrolysis apparatus for performing the method of the invention; and

FIG. 2 shows schematically a Soxhlet apparatus.

In the apparatus exemplified by FIG. 1, the anode 1 is constituted by the molten gallium on the bottom of the electrolytic cell. Current is supplied by a platinum wire 2 immersed in the gallium melt. The apparatus is equipped with a cathode 3 and with a catch funnel 4 beneath the cathode. The funnel 4 is connected with a storage vessel 5 through a capillary 6. The electrolyte 7 is kept in circulation by a thermosyph-on system comprising two legs 8 and 9. The leg 9 is surrounded by a cooler 10. The lower end of leg 8 forms a downwardly Widening funnel at 11 above the cathode 3. Connected to the circulating system is a return-flow cooler 12. The two legs 8 and 9 are interconnected by a transverse portion 13. During operation, the suction nippel 14 of the return-flow cooler 12 is 3,325,380 Patented June 13, 1967 "ice closed by a protective cap 15 to prevent contamination. A

provided in a conical and ground neck outlet 18 of the storage vessel to permit withdrawing the purified gallium 19. Another conical and ground closure is located at 20 and serves for introducing and sealing the cathode-current supply. Additional conical sealing junctions at 21 join the lower portion of the electrolytic cell with the top portion that comprises the entire circulating system described above.

The Soxhlet apparatus according to FIG. 2 comprises a middle portion 22, in which the extraction sleeve 23 with a gallium complex to be extracted is located. The middle portion 22 is upwardly closed by a cooler 24 and an adjacent drying tube 25. The downwardly closure of portion 23 is effected by a flask 26 in which the extraction agent is located.

The methods of producing and using electrolytes according to the invention may correspond to those described in my above-mentioned copending application. The following examples are applicable with the aid of devices as illustrated on the drawing.

For producing the complex Ga(AlBr,), commercially available aluminum is heated in a flow of nitrogen laden with bromine vapor. The resulting A1311, is converted to Ga(AlBr by adding metallic gallium. The complex is extracted with the aid of non-aqueous aromatic organic solvent, for example benzene, toluene or xylene, preferably using a Soxhlet as shown in FIG. 2 and described above. Thus the electrolyte required for the purposes of the invention is obtained. Due to the insolubility of many metal halogen compounds in the extraction agent, a considerable purification is already effected in this preparatory process.

Thereafter, the electrolysis resulting in the production of hyperpure gallium is performed in apparatus as shown in FIG. 1 and described above. Since the process is carried out in a completely closed vessel, contamination from the ambient atmosphere is prevented. The electrolysis can take place at the above-mentioned tem eratures below 50 C., which also minimizes the danger of contamination, particularly since the electrolyte is only slightly aggressive.

For performing the electrolysis, the quantity of cathode gallium required for starting the process is supplied through the vessel 5 so that the capillary 6 and the receiving funnel 4 are filled with gallium. The anode gallium 1 is supplied through the central nipple 17 in a quantity suificient to bring the level of the anode gallium to a height of at most a few millimeters below the lower end of tube 9. Thereafter, the electrolyte is filled into the vessel through the same nipple 17. Since the electrolyte must not be subjected to moisture, the filling must be done in a sealed container through a siphon or pump with the aid of a dry inert gas such as nitrogen. The electrolyte, for example, is composed of 50% by Weight of Ga(Al-Br and 50% benzene.

With nipple 17 open, the electrolyte is inducted through the suction nipple 14 up to the cock 16. Thereafter the clock 16 is closed, the suction line removed from nipple Aside from the addition of the anode gallium and the removal of the cathodically precipitated gallium, the device operates continuously and free of maintenance over long periods of time. After starting the process, the platinum wire of the cathode becomes coated with molten gallium until a drop of gallium is formed at the lower end and drips into the collecting funnel 4. This is repeated continually.

The precipitation is preferably carried out with a high cathode current density, preferably not below 200 amp/decimeter This is facilitated by the fact that the cathode surface is very small in comparison with the anode surface. However, the cathode current density may also be considerably lowered below the just-mentioned amount. Then the gallium is precipitated as a fine pulverulent metal applicable, for example, in the production of gallium-containing semiconducting sinter materials for thermoelectric purposes.

During operation, the heated electrolyte rises in the tube leg 8 and passes through the cooled leg 9 back to the lower portion of the cell. The considerable quantity of Joules heat generated in the vicinity of the cathode augments the thermo-syphon effect.

While the above-described example relates to a gallium aluminum-bromine complex, the invention is analogously applicable to gallium-aluminum complexes which contain other halogens, for example the complex Ga(AlCl or G a(AlI I claim:

1. The method of producing hyperpure gallium, which comprises electrolytically precipitating gallium from a solution of a gallium-aluminum complex of the type Ga(A1X wherein X is a halogen, in a non-aqueous organic solvent. 7

2. The method of producing hyperpure gallium, which comprises electrolytically precipitating gallium from a solution of the complex Ga(AlBr in a non-aqueous organic solvent.

References Cited UNITED STATES PATENTS 3.170.857 2/1965 Dotzer 20' --59 JOHN H. MACK, Primary Examiner.

H. S. WILLIAMS, Examiner. 

1. THE METHOD OF PRODUCING HYPERPURE GALLIUM, WHICH COMPRISES ELECTROLYTICALLY PRECIPITATING GALLIUM FROM A SOLUTION OF A GALLIUM-ALUMINUM COMPLEX OF THE TYPE GA(ALX4) WHEREIN X IS A HALOGEN, IN A NON-AQUEOUS ORGANIC SOLVENT. 